Question: $ { {-5} \times \left[\begin{array}{rr}{3} & {-1} \\ {4} & {-2} \\ {1} & {2}\end{array}\right] = {?} } $
Answer: To multiply a matrix by a number, multiply each item of the matrix by the number. ${\left[\begin{array}{rr}{-5}\times{3} & {-5}\times{-1} \\ {-5}\times{4} & {-5}\times{-2} \\ {-5}\times{1} & {-5}\times{2}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rr}{-15} & {5} \\ {-20} & {10} \\ {-5} & {-10}\end{array}\right]}$